Jump to content

Blower motor failure, removal, post mortem


heygibb

Recommended Posts

Hello. I'm new here but have been on the AACA forum since 2001, I believe. I'll try to contribute more w/ work I've done on my car that may be helpful in some way.

My blower motor failed the other day. It started normally when I turned the AC on but then a clunking sound halted the air flow. I opened up the plenum area and found lots of debris in there...pine straw, leaves, shop towel...yes, a shop towel. Anyway after removing the obstructions, I hooked blower motor back up and it won't run. It runs on the bench w/ 12v but not hooked up to harness plug for some reason. I tried to activate it w/ the AC controls, car running. I thought maybe I wasn't getting voltage to blower unit, from power module, so a probed terminals in harness connector w/ AC activated. I had 12.2v at the plug. Evidently there is enough resistance in the fan bearing to make it sketchy, so I will replace that. The squirrel cage does not have the resistance free feel of a new unit, that is for sure.

After insuring I had 12v at the plug, I shut the car off. When I got back under the hood, my VOM was still reading 12.2v at the plug. I'm guessing I fried the power module when the fan was stopped by the blockage. Does that sound about right? I don't think that terminal should be hot all the time. Before I replace the module, I thought I'd get more input.

 

1fandebris.JPG

 

3rag2.thumb.JPG.a04e41f6ef87eda966f82a3865599f89.JPG

5ragfan.thumb.JPG.eb11ae9fba4c099614944faa6c28cd71.JPG

hotlead.thumb.JPG.8449beaf420d4be25ffcf9819e44635c.JPG

Link to comment
Share on other sites

Welcome to the ROJ forum! I look forward to reading more of your posts. I'm amazed at what you found in the blower. Makes me think I need to check and see what I might find in mine. :)

Link to comment
Share on other sites

I am not sure what terminal is being measured at the blower module? It does get constant power to the module and when the module fails, it usually causes the fan to run all the time. At least that is the typical failure mode.

Link to comment
Share on other sites

I'm not clear on how you're testing. Do you have 12 volts going to the blower motor? This tutorial has some voltage tests in it that you might find useful in your troubleshooting: HVAC Programmer Test

Link to comment
Share on other sites

I am not sure what terminal is being measured at the blower module? It does get constant power to the module and when the module fails, it usually causes the fan to run all the time. At least that is the typical failure mode.

 

In the pic w/ the VOM, my leads are inserted in the connector that usually plugs into the blower motor.That leg comes from the power module. It has a constant 12v, w/out being instructed by the temp settings in the car. Since the consensus failure mode of the power module seems to be that the fan is running all the time, then this would do it. For some reason, it won't turn the fan when I reconnect it. My fan will run when bench tested w/ 12v but it's not immediate. I have to wiggle the leads at the battery to get the fan to turn over and run. It's worn out, I think.

Link to comment
Share on other sites

I'm not clear on how you're testing. Do you have 12 volts going to the blower motor? This tutorial has some voltage tests in it that you might find useful in your troubleshooting: HVAC Programmer Test

 

I'll look into that test. Does it help me determine whether module is faulty or not?

Link to comment
Share on other sites

 

I'll look into that test. Does it help me determine whether module is faulty or not?

 

The tests are really a reference of what my car was doing when the HVAC Programmer, which was working properly, was put through the paces to determine what signal it sends to the blower module to control it. The programmer tells the blower module what to do in order for the blower speed to change.

 

The tests don't actually tell you the blower module is bad because other factors could be causing the fan to not get proper power to make it operate. For instance you could have 12 volts at the fan connector as you do but the fan would not run if there wasn't enough amperage to power the blower motor due to a loose or dirty connection, bad fuse, etc. somewhere in the circuit. However, if that was the case you would see the voltage drop as soon as you apply a load to the circuit. Perhaps back-probing the fan motor connector for 12 volts with the blower motor connected might give you an indication of what is going on.

 

One of the failure modes of the blower module is you will have 12 volts going to the blower motor even when the ignition key is off.

Link to comment
Share on other sites

 

The tests are really a reference of what my car was doing when the HVAC Programmer, which was working properly, was put through the paces to determine what signal it sends to the blower module to control it. The programmer tells the blower module what to do in order for the blower speed to change.

 

The tests don't actually tell you the blower module is bad because other factors could be causing the fan to not get proper power to make it operate. For instance you could have 12 volts at the fan connector as you do but the fan would not run if there wasn't enough amperage to power the blower motor due to a loose or dirty connection, bad fuse, etc. somewhere in the circuit. However, if that was the case you would see the voltage drop as soon as you apply a load to the circuit. Perhaps back-probing the fan motor connector for 12 volts with the blower motor connected might give you an indication of what is going on.

 

 

One of the failure modes of the blower module is you will have 12 volts going to the blower motor even when the ignition key is off.

This is my situation...keys off, still 12v at blower motor terminal plug.

Your reference to inadequate amperage to initiate motor fan to turn makes sense. I'll probe the wires w/ while hooked up to the fan and see if there is a voltage drop under load. From what you know at this point, is it possible my power module is still good, and that the failure of the motor to turn on is due to worn out bearings/too much physical resistance from armature shaft to get it to turn? When I turn the squirrel cage, there is more resistance than I would expect from a freely turning armature. I have checked related fuses and relays but I will look again to make sure they are sound.

Link to comment
Share on other sites

It is possible that the blower module is still good but those things are notorious for going out. I would expect the blower motor to turn freely... with the exception of air resistance on the squirrel cage fan. Since your fan motor was stalled by all the debris in the fan you could have a bad blower motor, blower module or both.

 

Since the blower motor is the cheapest I would get a new one at Advance and try it. Most Advance auto parts stores will let you return electrical parts if you don't need them. Don't try that at your mom and pop parts store. A lot of them don't allow returns on electrical parts.

Link to comment
Share on other sites

I was thinking of going to a u pick parts yard maybe Friday. I'm collecting suitable GM cars w/ similar components from Rockauto database. I know the parts would be used and it's a gamble, but I might be able to get several. I'll look into the Advance Auto option. Good to know about their return policy on electrical parts. I'm familiar w/ some of those folks so that would help, also.

Link to comment
Share on other sites

Be sure to check the return policy of your local Advance store. The return policy might vary by location. My local Advance store has good people that are willing to work with you any way they can.

Link to comment
Share on other sites

As most every one knows I am a big parts swapper. I keep tested good parts on the shelf and swap in known good parts. This keeps me out of the repair manual which to me is combersome and hard to read. After 11 years and 250,000 miles I have had a lot of different "experiences" with these cars and have learned everything isn't as they seem.

At any rate here is what I have learned;

If the fan runs with the car off it is always the Blower Conrol Module.

If the fan does not come on or is a delayed start it is always the fan motor.

I buy used Blower Control Modules from my local You Pick but new fan motors from Auto Parts Stores.

Link to comment
Share on other sites

That approach makes a lot of sense. Thanks for that insight.

After Ronnie mentioned Advance for the blower motor, I checked it out. Low $20s makes getting new motor a no brainer. The module is another story. I was thinking of hitting salvage yard in next few days but I wanted to have new motor before trip so see how the power module reacted to it. My guess is that it's blown. My local AA and AZ don't have motor in stock so I'll have to wait.

 

From your experience, do you see any problem with transferring the old wheel (squirrel cage) to the new motor? Mine is still intact and appears to have small metal clips attached at particular vanes for balance, I'm guessing. I used to automatically think 'newer' is better, but after seeing how power tools have degraded in quality over the years, I don't know if a newer wheel would be actually better or not. Age is no friend of plastic so new appeals to me, but not if the quality of the new isn't there. Hope that makes sense.

Link to comment
Share on other sites

Dave may have had experience with changing the squirrel cage so his advice from experience might be better but if it were me I would spend a little extra and get one with a new squirrel cage already installed like this one. That way you don't  have to worry about balance or breaking yours removing it. Yours doesn't look too good to me.

Link to comment
Share on other sites

Good catch Ronnie. I buy the motor with the squirrel cage. Old plastic in close to the hotest part of the car leads to failure. You should also get more air movement which is a good thing.

Link to comment
Share on other sites

Dave is right about the greater air movement being a plus. The blower module is cooled by the airstream from the blower itself so I would guess that debris would tend to shorten its life?

Link to comment
Share on other sites

All good and welcome advice. If I was still working full time and this was a safety issue, like a brake component, I'd buy the whole deal and make the fix a sure thing. W/ fixed income, I have turned into one of those 'coupon clipper' people. If I can save a dollar, I usually do it. So, I'm going against consensus. After cleaning and inspecting the 'cage', I ordered just the motor from AZ...~$22 delivered to my doorstep. The same unit from Advance was about $4 more. AA is usually a little cheaper but the no shipping offer from AZ made the difference. I'm keeping the original vent tube.

The condition of the OEM unit convinced me it would be OK. The plastic/nylon is heavy duty. There aren't any divots in the outer edge from rubbing anywhere. The vanes are intact and aligned properly. The balance clips are tightly engaged w/ the vanes they are attached to.  When I lay the cage face down on a flat surface, it lays flat so there is no warpage that I detect. When I get the fan running on a bench test, there isn't significant wobble. If there ends up being a problem, I'll deal with it.

I'll get the motor next week sometime, I suppose. I'll report how it goes. Until then, I'll hold off on picking parts in relation to the power control module. I'll probably need that, too, but I try to troubleshoot one component at a time.

I look forward to the increased air movement, too, but it was pretty good all along. I never felt I was getting cheated on air flow. The fan was always super quiet. I expect it to be w/ the new motor, also. Getting the debris off the evaporator is a plus, for sure.

Link to comment
Share on other sites

:huh: :huh: Gonna check mine too.

Thanks for the post!

 

I meant to follow up on your comment. One thing I did differently from what the manual said re removing the fan. I moved the 'motor hanging loop' out of the way so I could remove the motor w/ fan cage attached. It's a 13mm nut. I removed the one closest to the motor completely and loosened the one on the other end so I could pivot it out of the way. The manual recommended to remove the cage from the motor while it's still half out of the housing enclosure. You may want to still do it that way yourself. I wanted full access for removal and replacement, w/ the unit intact.

One other thing, the sheet metal fire wall has a plastic covering on it. As I removed my motor, the mounting flange didn't want to release cleanly from the bottom of the opening. The plastic held on and cracked as I pivoted the motor out. If you are careful at that point in your removal, you could probably keep it from cracking. It's no big deal, since re-attachment will compress that plastic into place anyway, but I thought I'd let you know what happened to me.

enginelift.thumb.JPG.9dc648cf0c47371059ba1ddd9ab07361.JPG

blowerremoval.jpg.c70c993757d228a7f4863cf5ce82c239.jpg

bmotorremoval.jpg.d58f52ff65f0bfbcb69edc68b3760815.jpg

Link to comment
Share on other sites

W/ fixed income, I have turned into one of those 'coupon clipper' people. If I can save a dollar, I usually do it. So,

 

I can understand that. I'm in the same boat.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...